We’ve all had this happen. Most of us have fixed it by making the effort to understand what we’re doing, and also by realizing that anger is an enemy. Never work with computers when you are upset. Go outside, go for a walk, read a book, meditate, do calisthentics or yoga or something, and come back when you’ve calmed down.
Now. There is a partially completed download file. It’s located in the download directory that you specified when you began the task. That would be the default download directory that existed at the time unless you specified a different destination. Since you would have had to do that deliberately, you know where that is. Find the partial download.
Next, there is the .torrent file which is needed to start, continue and complete the transfer. You should have saved it to a known location. If you didn’t, you’re learning now why you should have. There is probably a copy of the .torrent in your /torrents subfolder. Find that and copy it somewhere you can find it again. I suggest you copy it to C:\Downloads\Torrents, (the location you’ll download all of your torrents to from now on, right? if you like you can move them to a /completed subfolder when you’re done, but don’t delete them until you’re absolutely certain that you’ll never need that .torrent again. Make cleaning up part of your monthly hygiene.) If there isn’t one, then there may be one in your torrent archive, which you can reactivate.
Open the torrent file using the menu, but don’t start it yet. (BTW, all of this is in the FAQ.), Now make sure that the download location is pointing to your partial download. Perform a manual hash check on it. This should take a while, then the % completed column should return to what you’d already downloaded. If it happens very quickly and the % completed column returns to zero, then you are pointing the download directory to the wrong place - or the partial file is not where you think it is. Try again. If your download is a directory, then you need to point to the directory that contains the directory you want. Play with it, you’ll get the hang of it quickly enough.
Once you’ve got it running, spend some time calmly browsing the wiki and the FAQ to get an idea of what’s in there. It’s good to read these things, even if you don’t remember any details, prior to an emergency. Then when one strikes, you’ll have some idea of where to go for answers.